Glass melting tank having a doghouse, and method for heating the charge material in such glass melting tanks

Abstract

A glass melting tank comprising at least one front part for introducing the charge material, and at least one charging device. To reduce atmospheric heat losses and reduce dust transport into the upper furnace of the tank, and nevertheless to intensify the heating of the charge material, the front part has a length “LV” of at least 2,250 mm in the direction of the melting tank, and a length “LG” of at least 1,200 mm is provided with an insulating roof. An end wall near the charging device, together with the roof, encloses a gas chamber open toward the melting tank. A characteristic value “K” of 3.50 tonnes (t) per hour and per square meter of surface is not exceeded. The characteristic value is calculated from P/F, where P is the throughput per hour in tonnes (t) and F is the inner surface of the front part in m.

The invention claimed is: 
     
       1. A glass melting tank for containing a glass melt having at least one doghouse for introduction of a charge material onto the glass melt and having at least one charging device, comprising:
 the glass melting tank having a rectangular shape, with a longitudinal axis, formed by sidewalls with a length dimension which is greater than a width dimension of end walls of the glass melting tank, 
 the at least one doghouse being arranged offset from the longitudinal axis of the glass melting tank,
 the at least one doghouse comprising side walls extending away from at least one of the walls forming the glass melting tank, and terminating in an outward direction at a lower end wall, and a bottom wall substantially co-planar with a bottom wall of the glass melting tank, the lower end wall having an upper boundary defining a plane closely adjacent, but above an upper surface of the glass melt, 
 
 the doghouse being sized and configured such that a transport path of the charge material in the doghouse is provided that is long enough so that the charge material in the doghouse is heated up to an at least partial melting by a flow of the glass melt below the upper surface of the glass melt back into the doghouse and by a penetration of thermal radiation from the melting tank into the doghouse, 
 the doghouse having an inner length dimension (LV) from the lower end wall to an inner edge of the at least one of the walls forming the glass melting tank of at least 2250 mm in a direction toward the melting tank, 
 the doghouse containing an insulating roof extending from the at least one of the walls forming the glass melting tank to an upper end wall spaced away from the at least one of the walls forming the glass melting tank, and having a length dimension (LG) of at least 70% of the inner length dimension (LV) of the doghouse, 
 the roof having the upper end wall oriented toward the charging device, said upper end wall enclosing, together with the roof, a gas chamber that is open toward the melting tank and being sufficiently large to permit the penetration of thermal radiation from the melting tank into the doghouse to effect the at least partial melting of the charge material within the doghouse, and 
 a throughput (P) of the charge material through the doghouse (in tonnes/hour) and an inner surface area (F) of the doghouse (in m 2 ), given a specified transport path, forming a ratio P/F that is known as the characteristic value (K), and based upon the dimensions (LV) and (LG) of the doghouse, a value of (K) is less than 3.50 t/h·m 2 . 
 
     
     
       2. The device as recited in  claim 1 , wherein the upper end wall has a lower edge that is situated above a plane in which an upper tank edge is situated, and that limits a charging gap. 
     
     
       3. The device as recited in  claim 2 , wherein the charging device has a periodically movable insert plate with which portions of charge material can be dosed through the charging gap into the doghouse and onto the melt. 
     
     
       4. The device as recited in  claim 1 , wherein the charging device has a screw conveyor by which the charge material can be dosed into the doghouse and onto the melt. 
     
     
       5. The device as recited in  claim 4 , wherein the screw conveyor has a housing that is set in sealed fashion into an end wall of the doghouse. 
     
     
       6. The device as recited in  claim 1 , wherein the doghouse roof is made so as to be curved upward in a longitudinal direction of the doghouse toward the melting tank. 
     
     
       7. The device as recited in  claim 1 , wherein the roof of the doghouse is made so as to be inclined upward in a direction toward the melting tank. 
     
     
       8. The device as recited in  claim 1 , wherein over a plane of an upper edge of the tank edge, the gas chamber has a height of at least 600 mm at a point along its length. 
     
     
       9. The device as recited in  claim 1 , wherein the doghouse has side walls that enclose between them an angle of from 0 to 45° that opens in a direction toward the melting tank. 
     
     
       10. The device as recited in  claim 1 , wherein the doghouse has at its inlet into the melting tank a width of at least 1000 mm. 
     
     
       11. A method for heating charge material on a glass melt in glass melting tanks having at least one doghouse being arranged offset from a longitudinal axis of the glass melting tank and having an inner length dimension (LV) and a length dimension (LG) and having a charging device for an introduction of the charge material, comprising the steps:
 heating and sintering the charge material in the doghouse from above by a penetration of thermal radiation from a tank chamber into a gas chamber in the doghouse, 
 heating and sintering the charge material in the doghouse from below by a flow and by a penetration of the glass melt back into the doghouse, up to an at least partial melting, 
 pushing the charge material onto a surface of the glass melt in the melting tank in an at least partly melted state, and 
 forming a ratio of a characteristic value (K) P/F between a throughput (P) of the charge material through the doghouse (in tonnes/hour) and an inner surface area (F) of the doghouse (in m 2 ), given a transport path through the doghouse according to the dimensions (LV) and (LG) of the doghouse, which does not exceed a value of 3.50 t/h·m 2 , 
 wherein the inner length dimension (LV) of the doghouse is from a lower end wall of the doghouse to an inner edge of at least one of the walls forming the glass melting tank, and 
 wherein the length dimension (LG) of the doghouse is from the at least one of the walls forming the glass melting tank to an upper end wall spaced away from the at least one of the walls forming the glass melting tank. 
 
     
     
       12. The method as recited in  claim 11 , including the step of selecting a transport path of the charge material in the doghouse in a range between 2.25 m and 5 m. 
     
     
       13. The method as recited in  claim 11 , including the step of selecting a width of the transport path of the charge material in the doghouse at an inlet into the melting tank of at least 1.0 m. 
     
     
       14. The method as recited in  claim 11 , including the step of selecting a position of the melt surface in the gas chamber such that there remains a minimum distance of 600 mm relative to a highest point of the roof of the dog house.